Electronic tube of the traveling wave type



Feb. 5, 1952 J. w. TlLEY ELECTRONIC TUBE OF THE TRAVELING WAVE TYPE Filed Jan. 28, 1948 INVENTOR. JOHN W 77253 ATTORNEYJ Patented Feb. 5, 1952 ELECTRONIC TUBE OF THE TRAVELING WAVE TYPE John W. Tiley, Philadelphia, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corpoi ration of Pennsylvania I Application January 28, 1948, Serial No. 4,849

13 Claims. (01. 315-39) This invention relates in general to the electron tube art, and more particularly to a novel electromagnetic traveling wave signal mixer or converter having special application'in high frequency and broad band electrical systems.

The present application shows an improvement of my co-pending patent application Serial No. 761,798, now Patent No. 2,541,843, filed July 18, 1947, and reference is made thereto. For further information, reference is also made to a previously filed continuation-in-part of the aforesaid application, Serial No. 761,798, namely my co-pending application Serial No. 788,724 filed November 28, 1947.

In order to facilitate understanding of the principles of the present invention, there follows a brief discussion of the general considerations involved in traveling wave electron tubes, which have been treated in detail in the co-pending patent applications enumerated above. This material is believed to provide ample background and information concerning the differences between traveling wave tubes and those tubes more common in prior art systems.

In'electrical systems such as television, pulseposition modulation and radar, it has often been extremely difficult to obtain adequate and uniform amplification and efiicient signal mixing and conversion over the frequency spectrum encompassed by the signal. when incorporated in special circuits, fail to provide a usable gain in such applications. Recent designs, such as the lighthouse tube, and the velocity modulation tube as exemplified by the klystron, can provide reasonable gain solely in narrow band width operation. An attemptto use a klystron or like tube in the microwave region with a band width of fifty megacycles or greater will result generally in a gain of less than unity. I

A recent electronic development, known as the beam traveling wave tube, overcomes the limitations of the more conventional tube types, and has previously been successfully tested as an efficient amplifier of signals having a mean frequency of the order of thousands of megacycles with an over-all band width of the order of eight hundred megacycles. Theoretically, even much wider bands may be amplified by the device Without sacrifice of gain.

For a description and illustration of this development, reference is made to the publication Bell Laboratories Record of December, 1946, and to the article therein entitled The Beam Traveling Wave Tube by J. R. Pierce. In this Ordinary triodes, even reference the traveling wave tube is described as constituted of an electron gun similar to those employed in cathode ray tubes. beam generated by the gun is directed in a narrow beam along the axis of a long evacuated tube and impinged upon a collector anode. Within the tube, and surrounding the beam axis, is a closely wound wire helix which is excited at the electron gun end thereof by the weak signal to be amplified and which provides at the collector end thereof the amplified output signal. The tube contains no signal grids in the conventional sense.

Broadly speaking, the applied signal travels along the wire helix as an electromagnetic wave at a speed approaching the speed of light. As is determined by the pitch of the helix. the wave travels axially of the tube at a fraction of the speed of light; and the electron gun and collector anode potentials are arranged so that the average axial velocity of the electron beam through the helix is somewhat greater than the axial wave velocity.

Interaction of the electron beam and electromagnetic field components extending from the helix produces the signal amplification. The greater the electron current and the longer the helix, the greater is the gain. In transit through the helix the average electron velocity is reduced, and the energy drop represented by this decreased velocity is imparted to the signal. The tube does not require a tuned circuit in the signal path, the wire helix being in effect an all pass transmission line. Hence the tube ,is capable of operation over an exceedingly wide frequency range. In practice this range is limited somewhat by the impedance match of the helix to the external circuits.

In operation the signal appearing on the helix acts on the electron stream and gradually. produces fluctuations in velocity and density. The density modulated electron beam delivers energy to the wave and over the helix section nearest the collector there is a substantially uniform gain per unit length of travel. 2

The present invention has as a primary object the provision of an electromagnetic traveling wave tube of novel and improved design, having wide application as a broad-band, high frequency mixer or high frequency converter. The electromagnetic traveling wave tube disclosed herein differs from prior art mixer and converter tubes in that means such as wave guides are utilized for directing signals around the path of An electron an electron beam for accomplishing the mixing operation. These guides, as disclosed in the above identified patent applications, permit direct coupling of the electromagnetic fields therein and the tube electron beam and preclude excessive energy radiation and undesirable coupling with external fields.

In the aforementioned patent application Serial No. 761,798, it was demonstrated that signal amplification could be obtained in an electromagnetic traveling wave :tube by causing .an electron beam to traverse the axis of first and second, or input and output helical wave guide sections of predetermined pitch and number of turns. The input wave guide was energized by the weak incoming signal, whereby the electron beam was bunched or density modulated. The modulated beam was then caused to traverse a second or output helicalwave guide section and to deliver energy thereto to provide the amplified output signal.

a tube of this construction, input and output wave guides are spaced axially of the electron beam. When certain. conditions of beam velocity and helix structure are properly satisfied, considerable gain is obtained and the electron tubes are.capable of either amplifier or cscillator operation; the latter being accomplished by coupling a predetermined portion of the out put signal in the correct phase to the input wave guide. I

In accordance with the principles of the present invention, means are provided for substantially simultaneously velocity modulating an electron beam by more than one traveling wave so that frequency conversion and frequency mixing is obtainable. In one form of this invention two input helical wave guides are coaxially arranged and interwo'und so that the electromagnetic wave" energy transmitted through these guides may substantially simultaneously coact upon an axial electron beam. The simultaneous action. of two signals upon a single electron beam may be considered effec- 'tive "as 'two simultaneous bunching operations,

and as 'a result thereof the density modulated electron beam contains components of the "sum and difference frequencies. A suitable output wave guide is provided 'for extracting energy from the bunched electron beam at either of these two frequencies, as desired.

'It is therefore an object of the present invention to provide a beam traveling wave electron tube for signal mixing or conversion which permits the simultaneous interaction 'of a p-lurality of electromagnetic signals and an electron beam.

Another object of the present invention .is to provide an electron tube having a plurality of interwound "co-axial helical Wave guide structures.

A still further object of the present invention is to provide a beam traveling wave electron tube, particularly adaptable for frequency mixing or conversion which permits maximum interaction between electrons in a beam and traveling wave high frequency energy.

Another object of the present invention is to provide a traveling wave type frequency mixer adapted to produce a sum or difference frequency signal from two electromagnetic waves of different frequencies.

A still further object of the present invention teraction and energy transfer with an electron beam.

These and other objects of the present invention will now become apparent from the following detailed specification when taken in c0nnection with the accompanying drawing which is a general side view partially in section, of a helical wave guide frequency mixer or converter.

With reference now to the drawing there is il- 'lustrated an electron tube incorporating the feature 'of the present invention and comprising, generally, alarge diameter glass or other dielectric cylinder 2i having tapered ends 22 and '23. The cylinder "25 is sealed off and evacuated. Sealed into the end 22 of the electron tube is an electron gun 28 similar to those utilized in con 'ventional cathode ray tube structures. As shown the electron gun 28 comprises a heater 29 and its associated cathode 3d, a centrally perforated control grid 25' and focusing and accelerating hollow cylindrical electrodes 25 and 26, respectively. when the electrodes comprising the electron gun it are energized from a suitable power source (not shown) an axial beai'n cflectrons of predetermined high velocity is generated and directed along the axis 28 of cylinder 2i toward a disc shaped collector electrode 2 sealed into the right-hand end of the tube as viewed in the'drawing.

Structural means required for supporting the electron gun electrodes have been omitted for clarity.

As the electron gun of the type included within the structure of the tube in the drawing is sufficiently 'well known in the electronic'art, a

further description thereof and of the energizing means therefor are considered unnecessary at this point.

In accordance withv the broad .principles of the present invention the axial path of travel of the electron beam through the tube 152i is substantially enclosed within a plurality of axially aligned helical wave guide structures. As illustrated in the drawing, two helical wave guide structures 3 and -32, herein designated as the input Wave guides, are in'te'rwound and co axially supported within the left-hand end of the tube. A third -co-axial 'he'lical wave guide 33, herein designated as "the output -heiical wave guide, is positioned between the 'interwcund input helical waveguides '31 and 3? and collector anode 27.

The precise means for supporting helical wave guides 3i, 32 and in the physical relationship is to provide a tube structure having a plurality of helical wave guides arranged for optimum inillustrated in the drawing has been omitted for purposes of simplification. It will be understood, however, that crinvention'a'l supporting means as used in numerous electron tubes may herein be correspondingly employed to secure all electrodes in thedesired relationship.

With the exception of differences in dimensions, the three helical wave guides 3|, 32 and 33, herein illustrated, are of similar construction. These wave guides are preferably formed of coils of unitary U-shaped metallic channels comprising, for example (reference being made to wave guide 32) metallic sidewalls and 36 rigidly spaced by integral outer metallic strip 31. As illustrated, each of the open faces of the U-shaped channels constituting the wave guides '31, 32 and 33 is formed to define a cylinder. The cylinders defined by the inner edges of wave guides 3| and 32 are coincident and co-axial with the cylinder defined by the inner edges of output wave guide 33. "The differences in pitch of the helical wave in considerable detail in the aforementioned patent applications and for this reasonare not considered in greater detail herein.

Electromagnetic wave energy at the desired frequency may be introduced into the helical wave guides 3| and 32 through co-axial lines 4| and 42, respectively. As illustrated in thedrawing, the

outerconduc'tor of each of co-axial lines 4| and 42 extends through the dielectric cylinder 2| and enters its respective helical wave guide through the outer helical metallic strip thereof. Coupling loops 43 and 44 formed of the co-axial line inner conductors'provide ample signal coupling to the regions within the helical wave guides. In a corresponding manner, a co-axial cable 46 is utilized to extract signal energy from the output helical wave guide 33. As illustrated in the drawing,the outer conductor of co-axial cable 46 extends throughthe dielectric cylinder 2| and in through the outer edge of wave guide 33. A small loop 4l-formed in the inner conductor serves as the signal coupling between the co-axial cable 46 and the wave guide 33.

The outer surface of I the dielectric cylinder 2| between coupling co-axial cables 42 and 46'is substantially enclosed within a cylindrical coil form upon which a uniform solenoid type coil 52 is wound. When coil 52 is energized from a direct current source (not shown) a magnetic field is established having a large component parallel to the electron beam axis which is directed from the electron gun 23 to the collector anode 21. This magnetic field minimizes de-focusing of the electron beam in itscomparatively long axial transit through the cylinder 2|. In the discussion below of the operation of this tube, it will be understood that the solenoid coil 52 is energized and thereby maintaining the aforementioned axially magnetic field. 1

Broadly speaking, and prior to entering upon a discussion of the particular dimensions of the Waveguide components illustrated, mixer operation of the electron tube shown in the drawing is as follows. Microwave energy at the two frequencies to be mixed is applied through co-axial cables 4| and 42 to energize helical wave guides 3| and 32 respectively which together comprise I the input section of the electron tube. These input signals travel down the helical waveguides 3| and 32in the direction of flow of electrons in beam toward electrode 21. The actual axial velocity of each of the traveling waves is a fraction of the propagation velocity through these wave guides due to the helical path traversed. ,The aforementioned dissipative blocks secured within the ends of all wave guide sections ensure the absence of traveling waves in a direction other than the axial direction of electron flow.

Between any two opposed points, such as M and N of the opensided helical wave guide 3| and points P and Q of wave guide 32 electric fields are established which have components within the tube parallel to the axis 28 of electron flow. These electric field components may bevisualized as spinning about the axis of the tube at somewhat less than the velocity of light as the waves travel from left to right as viewed in the drawing. The electron beam, in traversing the inputsection of the tube comprising wave guides 3| and 32, is bunched in accordance with the intensity variation of both applied signals. This bunching operation is, in effect, density modulation of electron beam, which modulation includes components equal in frequency to the sum and difference of the applied signal in addition to frequency components equal to those of the applied signals. Thus the electron beam emerges from the space between the input section comprising helical wave guides 3| and 32 and the output v helical wave guide as a comparatively high energy bunched beam. Upon entering the region of the electron tube spanned by the output helical wave guide 33 the bunched electron beam is retarded somewhat and thereby delivers energy to the wave guide 33 by excitation of a traveling wave therein which progresses at a speed approaching the speed of light toward the output coupling loop 4'! of co-axial cable 46.

The frequenc of the output signal induced in wave guide 33 and delivered at co-axial cable 46 may be selected simply by arranging the dimensions of wave guide 33 for suitable response to the desired signal frequency, a component of which appears in the bunched beam. In the drawing, the output wave guide 33 is illustrated as one responsive to a frequency equal to the sum of the signal frequencies applied at co-axial cables 4| and 42.

In accordance with the principles described in the aforementioned parent patent application (but not shown herein) the pitch of the output helical wave guide 33 may be progressively diminished as it approaches elector electrode 21. In this manner maximum energy may be extracted from the bunched electron beam and delivered over co-axial cable 46 to a suitable load circuit (not shown).

The helical wave guides 3| and 32 of the tube input section are proportioned to pass the frequencies applied at co-axial cables 4! and 42. It will be noted that the physical dimensions of wave guide 32 are smaller than the corresponding .dimensions for wave guide 3|, indicating that the frequency of operation of guide 32 is higher than that of guide 3|. Since output helical wave guide 33 is herein designed for the purpose of extracting a sum frequency, its dimensions are correspondingly smaller than those of helical wave guides 3| and 32.

It is preferable that the two input wave guides 3| and 32 be arranged to provide for slightly different axial velocities of the electromagnetic wave traveling therethrough. The drawing illustrates one manner in which this particular relationship between axial components of the traveling wave may be established. Thus, wave guides 3| and 32 are proportioned to give-the same velocity propagation as measured helically around each guide, but the pitch of helical wave guide 32 is somewhat greater than the pitch of guide 3|. Thus, note that there are six active turns of helical wave guide 32 to the right of coaxial coupler 42 for seven active turns of helical wave guide 3| measured to the right of co-axial cable 4|. Since the space occupied by these, active turns of helical wave guides 3| and 32 is substantially the same and further, since as above mentioned, the velocity of propagation as measured around the helices is equal for both, then assesses 7 it follows theaxial velocity componentsiiofirtheraa: wavesW-in both guids are' soinewhatj: differ-en Since output helical wave guide 33 is proportioned to transmit the" sum of the frequeneies ap plied to wave guidesfil and' 32 :it preferably con- 5 tains a number of active turnsin a given len'gth thereof equal-:to the-sum ofzthe active'turns of waveguides 3i ancl-32for the same lengthc By arranging for different axial :veloeitie's of propagation through helical wave guides-"3! and: 32 OPtiIhUm operating "efficiency i obtained?" Tlfiisflnote that if the axial velocities of both' waves in helical waveguides 3l andSZi/vere 'the sameand qual -to the average electron velocity-.2 in the eleetron beam :it would be possible that 15. an electron or group' -of #electrons" could pass through the entir'e input section -of the tube as spanned by waveguidestl an'dBZ without-afiecti thereon by the wave energy extending i into the region of the electron-beam from'either of the helical wave guides. For best resultsgit is 'desirable T that each electronin-the beam 'be acted: upon'by at lea'stone of the two electro' rnagnetic waves and preferably byboth' By assuringj'in accordance 'with the-structure illustrated in the i drawing,- that the" axial velocities of -t'h'e travering" waves" through 'guides El and :32 'are difierent; then"-interaction between each electron f and. at'l'east one of the traveling fields is certain.

8 The Y microwave mixerfland v converte1-' electron tube illustrated in the drawing is of particular"-' advantageq-in high-jfrequency systems-;- in that the band of operation covere d isextremelybroad-gfurthermore; "that-amplification" is obtained dur ing the mixing or z'COl'lVBISiOIl"DIOCESSW" Signalamplificationin microwave mixers or converters is ofparticulan advantage to -microwave system engineering,=since crystalsj-and like rectifying elements ordinarily used for mixing and conver-'- sion -intr0ducedecided f energy loss ratherthan signal level i gain; 7 Although the electron"- tube of Figure I has-been illustrated as providing an output signal equal"*- infrequencyto the sum: ofapplied signalfre; quencies it is evident" that the difierence ire-" quency may be"obtained-by'proportioning output helical--waveguide 33 iso-that =it is capable-"017 transmitting z'the difierence frequency. This would requirethatthe pitch of -the-wave guide 33- be such-=that for-a given length it contains-a number of turns corresponding to the difference of the number'of turnsof helical;waveguides--31- and32; for'the-same-length; It is to be mentioned---- at this --point that traveling; .wave electron; tubes neednot be utilized *for -lowering a system -free quency as gain at high frequencies can be secured.;-- H V V The-various features described inconsiderable- It is desirable; therefore; that the average velocity 39 ggg fi ifigg fgg sg ffigggggg g2 32215355 ofelectrons in the electron'beam 28 be-equal to I the mean or the axial velocities of the traveling al ggg g g 35556112 011. waves in helical-wa've guidesand 329 The i I j if axial velocity of an electron in the beam is, of of hegcal s g? Pd-:3 'W j course'padjustable byvariation of the potentials gfiggfi gpwfi fi g igg gi 533 5222: ggg ig of "the" electron gunv and collector" electrode 21. i t when the average electron velocitylies between gaolfgossy substai ce to preclude waves 'and guides 31 and 32 "the interchange of a energy; between traveling waves and electron 4:5 sigliistfance will precludeoscillatiorr and--undes1rbeam Wm have'mmi'mum efiebt mm theiavemgeq a i s i l iflentthat various modifications of velocity of an electron in the beamfi L i. I

may serve as a frequency converter inaddition I to a irquency mixer as abovedescribedfi A frezgz sg quency 'converten -as is -wel'l -understoodg is es-" endediclaim y Y 'scop P--- sentially a combination of a mixer anda local p I i oscillator. Asdes'cribed in considerable detail 1 A tm in the aforementioned'patent applications a team in gg l gg ec g 59 l; traveling Wave electron'tube may be used as an -5 velope anelectron gun r gggz w e n; oscillator by coupling a predetermined fraction? saidl-envrelope g an fig g g glfirilgslssignal output back to its signal input terof pr erm g gi eq dn y"a o an b? a 3 ?'?Rm simply 9y m generated electron-beam axially throughsaiden; ingthe teiinination of the helical wave guide so velopeimpingm Said 1 asztfoproviie reflections of hat .ampmude'anq. lector'electi'ode 'me ns -dispos :l j ac e n t;id phase necessary to cause oscillation. A prefer lebtr n'g 'foi veloc tymodul atin said 81 I able na a suitable QQ kfi tron beam simultaneouslydn accordaice' 'with t f ;m electron f? r ing Wave 60 least twosignals and com'prisinga pair of intereleqtlon W ls t6 9 9 of the Output" T woundlielicalwav guides said waveguide each energy from the output coupler of-the" tubeback pr ifi f 'h nnm ap n u t r i s b to theinput coupler thereof through resonant stafifiauy rectafigmar: g g t path 9 t fgd ends of each of said 'c hanr'iel'shaped conductors frequency. lhis typeof coupling 1; sufiicient in i cylindrical surface 6 maxi M with said. w q e'k gw egap l p e h ndl electron beam, m ans for intredueingmerewave' by'an e ectlonfube F QQ r energy at predetermined frequencies to said in er 3 of pcslble means r 1 terwoundhelical wave guides'for establishi'rlg' npi ap -no o he electron tube traveling waves therein, said interwound' helical shown in the-brewing are not fill/'61! herein. wave guidesperniitting theinteraction of micro: Howevenwhen such self-oscillation is established wave energy flowing' therein" and said" electron this oscillation will provide one of-thetwo frebeam. quencies to be mixed. The second of thefre- 2. A beam travelingwave electron'tubeco i quencies to be mixed-may be applied at-one-ofprising in combination within an "evacuated'e the "co-axlallines it or 42.

said envelope for generating an electron beam of predetermined average electron velocity, a collector electrode positioned within the opposed end of said envelope, means for directing said generated electron beam axially through said envelope. and impinging said beam upon said collector electrode, means disposed adjacent said electron gun for velocity modulating said electron beam simultaneously in accordance with at least two signals and comprising a pair of interwound heli-ei' cal wave guides, said wave guidesv each comprising channel shaped conductors of substantially rectangular cross-section, the open ends of each of said channel shaped conductors defining a cylindrical surface coaxial with said electrona' beam, means for introducing microwave energy at predetermined frequencies to said interwound helical wave guides for establishing traveling waves therein, said interwound helical wave guides permitting the interaction of microwave??? energy flowing therein and said electron beam, means disposed between said interwound helical wave guides and said collector electrode adapted to extract energy from an electron beam velocity modulated by energy flow in said interwoundw helical wave guides comprising a third helical wave guide co-axial with said interwound wave guides and formed substantially as each of said interwound wave guides, said third helical wave guide being adapted to propagate microwave energy at a frequency equal to the sum or difference of said predetermined frequencies.

3. A beam traveling wave electron tube comprising in combination within an evacuated envelope, an electron gun disposed at one end of least two signals and comprising a pair of interwound helical wave guides, said wave guides each comprising channel shaped conductors of substantially rectangular cross-section, the open ends of each of said channel shaped conductors defining a cylindrical surface co-axial with saidv electron beam, means for introducing microwave energy at predetermined frequencies to said interwound helical wave guides for establishing traveling waves therein, said interwound helical wave guides permitting the interaction of micron, wave energy flowing therein and said electron" beam, means disposed between said interwound helical wave guides and said collector electrode adapted to extract energy from an electron beam density modulated by energy flow in said interwound helical wave guides comprising a third helical waveguide. co-axial with said interwound wave guides and formed substantially as each of said interwound wave guides, said third helical wave guides being adapted to propagate microwave energy at a frequency equal to the sum or difference of said predetermined frequencies, the pitches of said interwound helical wave guides being different, the number of turns for a given length of said third helical wave guide being equal to the sum or difference of the number of 70 turns of said two interwound wave guides for the same length.

4. 'A beam traveling wave electron tube comprising in combination within an evacuated en- 1o of said envelope, an electron collector positioned within the opposite end of said envelope, a first wave guide of a predetermined pitch surrounding a portion of the axial path from said source to said collector, means for exciting said first wave guide by an input signal of a predetermined frequency, a second waveguide of a predetermined pitch surrounding a portion of the axial path from said source to said collector, means for exciting said second wave guide by an input signal of a predetermined frequency, and athirdiwave guide of a predetermined pitch surrounding a portion of the axial path from saidsourceto said collector, said third waveguide beingaxially displaced from said first and second wave guides, and means for extracting signal energyfrom said third wave guide in-accordance'with saidinput signals.

"55A beam traveling wave electron tube comprising in combination within 'an-evacuatedenvelope, a source of electrons disposedat-one-end of said envelope, an electron collector positioned within the opposite end ofsaid envelope; a first wave guide of a predetermined pitch surrounding a portion of the axial path from said source to said collector, means for exciting said first wave guide by an input signal-of a predetermined frequency a second wave guide -of-a-pitch different than the pitch of said first'wave guide,-and a third wave guide means for exciting said second wave guide by an-input signal of a 'predetermined frequency, of a predetermined pitch surrounding a portion ofthe axialpath-fromsaid source to said rcollector, said third wave guide being axially displaced-from said first and second wave guides, and means for-extracting signal energy from said third waveguide-inaccordance with said'input signals.z g 1 6-. Abeam traveling wave electrontube comprising in combination within an evacuated envelope, a source of electrons disposedat-one end of said envelope, an electron collector positioned within the opposite end'of' said envelope; afirst wave guide of a-predetermined pitch-surrounding a portion of the axial path from said source to said collector, a second wave guide of 'a'pitch difierent' than the pitch of said first'wave guide, and a third wave guide of a predeterminedpitch surrounding a portion of the axial path frorri'said source "to said collector, said 'third' wave guide being axially displaced from said'first and second Wave guidesQthe' portion of the waveguide adjacent the axial path of' said electron beam being open to provide coupling between 'theele'ctromagnetic energy in said wave guides and said electron beam. I g i 7. A beam traveling wave electron tube comprising in combination within an evacuated envelope, a source of electrons dispo'sed'atone end 4-00 of said envelope, an electron collectorpositioned within the opposite end of said envelope, a first wave guide'of a predeterminedpitch surrounding a portion of the axial path from said source to said collector, a second waveguide of a pre- '65 determined pitch surrounding a portion of the axial path from said source to said collector, and a third wave guide of apredetermined pitch surrounding a portion of the axial path from said source to said collector, said third wave guide being axially displaced from said. firsta-nd second wave guides, the portion of thewave guide adjacent the axial path of said electron beam being open to provide coupling between the electromagnetic energy in said wave guides and said velope, a source of electrons disposed at one end 15 electron beam.

. as aeos 8, A peamtrayeling; wave, electron 7 tube ,comprisingcombinationlwithin an evaouated; en- 'fj'i lope a source of .electrons disposed. at, one (end For-said envelope, an electron collector positioned u'faire "guide of 'a predetermined pitch surroundi 'ing ap'ortion fof th axial path-from said source ftpsid collector, asecond'wave' guide .of a pree'termined pitch"'surrounding "a portion of the ai'tlfird wave "guide ."of"a"'predetermined pitch siiri'bunding af'p'orti'on 'ofthe axial path from aid"s'oufce"to"'said' collector; said 'third wave uide beingaxially displaced from said first and tne axialjpath of said: electron beam er'ftii p'r'ovi'de coupling 'b'etweenthe eleci dal'path 'from saidsourceto said collector, and jo ave guides) the portiofrof tlie wave guide;

-i011 establishing said electricfields w itl in said .fiube. parallel to thehaxis' of the electri field-I01 d nsity modu ati ethee lctr nlbeemt n a c rd- ,ance With the .isien ih ensities,,said ,electt I beam ,when entering the region, of vsaid tube p ned by, a dputput eli ll wave u de-bein grfltmded and delivering energy tq saidiwavg guide 1: Beam; a .plur'ality of input? 'inte'riwound ...coaxial helicalmetallirwave g'uidesinounted in.:one.1end V 101', said tub ,fari output coaxial. helic l wave uide 1..positi.onejd :in said, tu ih tweenlsaid; interwqund g input av guides.andlcq lect el etr deieac 1101.saidwemguldeswmvnifin .met l e w s --:.I1e ne.a ePn.I e p finin a qy ind r which non/Si. tes aidagsial a spaced by an integral outer metallic and I. .byvexcitation foirthelt evelling wave t ene na means ior. ext a tin i nal. ener y om @the output helical wfilv hguide. Y

a 12. lAn eleqtrontube haying? cathqdelfougenerating an electron lqeam along an axial path of e, semi-tube a cql e or,elec rod -hr sa d ectmn beam, a plurality 4 of- .input v inter-wound coaxial helical. metallic- ,wave guidesmounted ,inflone, end of said tube, anoutput, coaxial helical waveguide positioned in sa deub lbetweenl aid interw und input wave guides and collector electrode, said ,wave l guides having an open portion forming said lel et n b am pa h. coupl ng mean r; i troducing. electromagnetic ,wave energy .at Ztl e, delivered-fre ue c int e ea h; f -aid .p1 r i y 0 v np ,waverguide asa d wave. nergy-rtravellin v alqng said wave vgu des inltheection oi said vl-ele t o be o l stnh shin sa d electr c fields 0 w th n s tub wp ra lel .tetheax sof the.:.e1.ectnc V fie for den y. m du e n tnee ec mn beam in accordan e w t ethe s n in en iti s idrelecrtron peamwhem tering the regionof said tube V spann d b said. outpu el c lnwav vguide ,bein reta de and-ddilfifill ene tor-said wa uid q excitationof the trayelling waye-therein and means for, extracting..signal energyfromvthe outlputheli lw ye i 1 Anelectmntu .llflllil l fi t ifle ffllt genezzefineaueleetrp Bean len la axial nathvo tupe a collector electred for saidfl electron m, a plurality pf input rnterwqund coaxial iealmetallic wave guidflsmounted inflone-end 1 id tu be, an eutput cpaxial helical wave guide erred in said tube. between said 7 interwound p11 were. guides andicollector. electrode, coupling means for introducing electromagneticwave energy at the desired frequencies intd eacliof said plutality of input v'vave guides, and means for extracting signal energy from "tputjhelicai wave guide;'

:EQE WE REFERENCES-CITED a The following referer g es are of record in the llictthisl patentt NI'IE SI EESRA'FEN' IS 

